Boat Wiring Pages

Troubleshooting Marine Electrical

Introduction

Is there anything more frustrating than a breakdown? Without warning, a
trusted piece of equipment just quits working! There is something more
frustrating ...that tool you need to fix the problem is sitting at home in the
tool box!

Breakdowns always seem to happen at the worst possible moment, and having the
right tool to fix the problem doesn't help the initial feeling of letdown. But,
when the dust settles, and it's either fix the problem or call the repair
technican, having the right tool onboard makes the decision a little easier. If
there isn't a technican to be called, frustration at leaving the right tool
behind will be strong.

Considering the number of connections, wires and other components in an
electrical system, reliability is quite good for most installations. We've seen
many systems that makes us wonder if neat wiring with appropriate connections
aren't just a waste of money ... if this system runs, anything will!

Failures can be expected in systems where the installation practices were
poor, and little or no maintenance has taken place, but even the best installed
equipment will fail. What does it take to fix an electrical failure?

A Sharp Set of
Eyes

Electrical failures are often the result of a mechanical failure. A broken
splice, a loose crimp lug, or a missing screw in a terminal block can interrupt
electricity and your vacation.

Knowing what to look for is the first hurdle. Don't you wish you'd made a
list of all the terminals that had wires on them before the trouble began?
Wouldn't it be nice if all the wires were labelled and you knew where each of
them went?

In a large system, knowing all the wires and their function can only be done
a piece at a time, and only be someone highly skilled in the trade. However,
it's a good idea to inspect the system when it works so you won't be so daunted
by it all when it fails.

A Digital
Voltmeter

Many years ago we were driving an old pickup in the desert east of San Diego,
CA. We'd been camping miles from the nearest paved road and hadn't seen any
other people for 3 days. Without warning, the truck quit running. Inspection of
the distributer gave us the answer ...the rubbing block on the points had
broken.

A spare set was in the toolbox, and minutes later we were ready to set the
timing and be on our way. There was only one problem ...the voltmeter I used to
indicate when the points actually opened was at home! After swearing, kicking
the tires a bit, and fruitlessly trying to eyeball the difference between open
and closed points at the timing point, some semblence of rational thought
returned. My companion smoked, and cigarette paper was a thin insulator that
worked between the point to indicate when the points gripped the paper,
(closed), and when the points released the grip, (open). A voltmeter has been
standard in my toolbox ever since!

Learning how to use a voltmeter is almost as simple as learning how to read a
thermometer, or tell time using a digital watch! Don't know what a Volt is? So
what, other than keeping everything from happening at once, even science can't
explain time.

Not knowing what to do with the information derived from the voltmeter is a
more serious problem. However, perhaps you can contact a technican by phone or
radio and have them tell you what to measure and what it means! Telling a tech
that a light doesn't work isn't very illuminating ...telling him that there is
voltage on one side of the light and not on the other may get the light to go on
over the tech's head.

Here's a simple test that anyone can make. An external alternator regulator
is enabled from the ignition switch, or an oil pressure switch. Find that wire
by measuring voltage on all the pins of the regulator with the ignition switch
off and then with it on. You should find a wire that has voltage on it when the
ignition switch is on and no voltage with the switch off. You will probably find
two such wires if the regulator works ...one of them is the field wire going to
the alternator.

Digital voltmeters are fairly inexpensive, and should be in every toolbox!
Learn how to take readings ...you may even surprise yourself and learn a little
about electricity while you're at it. You can't usually hear or see electricity,
so when it comes to explaining symptoms to a long distance tech, nothing is
better than a simple voltmeter.

A Clamp-On
Ammeter

Voltage readings can be used to tell if a battery is being charged or
discharged, but if you want to know how fast, you need an ammeter. Ammeters are
made that have opening jaws so that they can be `clamped' over a wire. They
don't really clamp onto the wire, rather the wire goes through the center of the
jaws. Once clamped over a wire, the jaws measure the strength of the magnetic
field produced by flowing current, and translate the measurement into Amps.

If you want to know how well the alternator or battery charger is operating,
the ammeter is the tool. Want to know how much the inverter draws with the
microwave cooking? The ammeter can tell you.